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Generalized Bhaskar Rao Designs with Block Size 4 Signed over Elementary Abelian Groups

Gennian Ge1, Malcolm Greig2, Jennifer Seberry3
1Department of Mathematics, Suzhou University, Suzhou, 215006, P. R. China
2Greig Consulting, 317-130 East 11th St., North Vancouver, BC, Canada V7L 4R3
3School of Information Technology and Computer Science, University of Wollongong, Wollongong, NSW 2522, Australia.

Abstract

De Launey and Seberry have looked at the existence of Generalized Bhaskar Rao designs with block size 4 signed over elementary Abelian groups and shown that the necessary conditions for the existence of a \( (v, 4, \lambda; EA(g)) \) GBRD are sufficient for \( \lambda > g \) with 70 possible basic exceptions. This article extends that work by reducing those possible exceptions to just a \( (9, 4, 18h; EA(9h)) \) GBRD, where \( \gcd(6, h) = 1 \), and shows that for \( \lambda = g \) the necessary conditions are sufficient for \( v > 46 \).

Keywords: Generalized Bhaskar Rao design, Group divisible design. AMS subject classification: 05B05.